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A231050 Number of 2 X n 0..3 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero. 1
0, 2, 14, 32, 100, 428, 1616, 5784, 21248, 78840, 290776, 1070552, 3946728, 14554440, 53657032, 197805128, 729249064, 2688543176, 9911794984, 36541580104, 134717359592, 496660701448, 1831031342376, 6750435204552, 24886729062376 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 3*a(n-1) + 8*a(n-3) + 6*a(n-4) - 4*a(n-5) for n>6.

Empirical g.f.: 2*x^2*(1 + x)*(1 + 3*x - 8*x^2 + 2*x^3) / (1 - 3*x - 8*x^3 - 6*x^4 + 4*x^5). - Colin Barker, Sep 26 2018

EXAMPLE

Some solutions for n=4:

..0..3..0..3....0..3..2..3....0..1..2..3....0..3..0..3....0..3..2..3

..2..1..2..1....0..1..0..1....2..3..0..3....0..1..2..1....2..1..0..1

CROSSREFS

Row 2 of A231049.

Sequence in context: A294558 A202638 A226565 * A322074 A083015 A282036

Adjacent sequences:  A231047 A231048 A231049 * A231051 A231052 A231053

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 03 2013

STATUS

approved

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Last modified November 20 10:09 EST 2019. Contains 329334 sequences. (Running on oeis4.)